Die apparatus, method for producing perforated work plate, perforated work plate, liquid-jet head and liquid-jet apparatus

ABSTRACT

A die apparatus is composed of a lower receiving die, a round punch having the shape of a fine hole, and PET provided between the lower receiving die and the round punch. The round punch is passed through a work plate placed on the PET to cause a punched-out piece to remain within the PET, thereby boring the fine hole. The work plate having such fine holes is thus easily prepared, and applied as a filter for a liquid-jet head.

The entire disclosure of Japanese Patent Application Nos. 2005-092286 filed Mar. 28, 2005 and 2005-096909 filed Mar. 30, 2005 is expressly incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a die apparatus for boring fine holes, which are through-holes, in an ultrathin plate as a work plate. The die apparatus is preferred for application to the preparation of a filter for a liquid-jet head for trapping foreign matter contained in a liquid to be supplied to a pressure generating chamber of the liquid-jet head.

The present invention also relates to a method for producing a perforated work plate having fine holes, which are through-holes, bored in an ultrathin plate as a work plate. This method is preferred for application to the production of a perforated ultrathin plate for use as a filter for a liquid-jet head for trapping foreign matter contained in a liquid to be supplied to a pressure generating chamber of the liquid-jet head.

The present invention also relates to a perforated work plate having fine holes, which are through-holes, bored in an ultrathin plate. This perforated work plate is preferred for application to a filter for a liquid-jet head for trapping foreign matter contained in a liquid to be supplied to a pressure generating chamber of the liquid-jet head.

The present invention further relates to a liquid-jet head including a filter having fine holes, which are through-holes, bored in an ultrathin plate, the filter being used as a filter for a liquid-jet head, and a liquid-jet apparatus including the liquid-jet head.

2. Description of the Related Art

Liquid-jet apparatuses are designed to jet various liquids, and an ink-jet recording apparatus, in particular, is used widely. The ink-jet recording apparatus has an ink-jet head for ejecting ink droplets, which are liquids, through a plurality of nozzle orifices. By the action of the ink-jet head, ink droplets are caused to impinge on the surface of a recording sheet or the like, which is a medium, thereby printing images or characters thereon.

In the ink supply passage provided in the ink-jet head, a flat plate-shaped filter is disposed for removing foreign matter intruding into ink, namely, fine pieces of synthetic resin or air bubbles remaining within the supply passage for some unknown cause. As such a filter, a twilled filter or a nonwoven fabric filter is usually adopted (see Japanese Patent Application Laid-Open No. 1999-10904).

However, the twilled filter has a low opening rate and involves a great pressure loss (passage resistance), so that it has been customary practice to increase the area of the filter. This practice, however, increases the size of the filter, making it difficult to downsize the ink-jet head. Moreover, the shape of the passage within the filter is so complicated that the pressure loss varies with each filter. Accommodating such variations within the tolerance range is difficult, thereby destabilizing the ability to trap foreign matter. Furthermore, the edge portion of the filter is frayed, thus causing a tendency toward damage to components, for example, during the step of assembling the filter. This poses difficulty in handling of the filter, and brings disadvantage to costs. With the nonwoven fabric, fine pieces of fiber are likely to flow downward together with ink from the filter, deteriorating reliability.

Under these circumstances, it has been contemplated to use a filter having many fine holes (for example, holes of 15 μm in diameter) formed in an ultrathin metal plate (for example, SUS plate of 10 to 20 μm in thickness) by punching. By using as the filter such an ultrathin metal plate having many fine holes formed therein, it becomes possible to decrease the pressure loss, ensure an adequate flow rate of ink, and impart a stable function of trapping foreign matter.

In preparing the ultrathin metal plate having many fine holes formed therein, it is conceivable to use a die apparatus comprising an upper die (punch) having the same diameter as that of the fine hole, and a lower die (die) having a depression (for example, a hole having a diameter of 16 to 17 μm) slightly larger in diameter than the fine hole, and pass the punch through the ultrathin metal plate with the use of the depression of the die as a pad to carry out punching.

To allow the ultrathin metal plate to function as a filter, it is necessary to provide the ultrathin metal plate with many of the fine holes (for example, several tens of thousands of the holes/cm²), thus requiring that fine depressions be formed in the die. In actual manufacturing, many of the fine holes need to be punched at a time, and many of the fine depressions should be formed in the die. Moreover, alignment of the punch and the die (concentricity 1 μm or less) is difficult.

It presents a tremendous difficulty to form many such fine depressions in the die, or to perform fine alignment corresponding to concentricity of 1 μm or less. Actually, serious difficulty is encountered in preparing an ultrathin metal plate having many fine holes formed therein by use of the punches and the die having the depressions. Besides, it is expected that the depressions of the die will be clogged with slugs, or the depressions will be covered with slugs, whereby tiny damages to the die may be caused.

Accordingly, no technologies have been established for applying an ultrathin metal plate, which has many fine holes formed therein, to a filter for a liquid-jet head.

SUMMARY OF THE INVENTION

The present invention has been accomplished in the light of the foregoing situations. It is an object of the present invention to provide a die apparatus capable of easily preparing an ultrathin metal plate which is a work plate having many fine holes formed therein.

Also, the present invention has been accomplished in the light of the above-mentioned situations. It is another object of the present invention to provide a method for producing a perforated work plate, which can easily prepare an ultrathin metal plate being a work plate having many fine holes formed therein.

Moreover, the present invention has been accomplished in the light of the aforementioned situations. It is still another object of the present invention to provide a perforated work plate, which minimizes a pressure loss and ensures an adequate flow rate of ink, which can perform a stable function of trapping foreign matter, and which can be applied as an easy-to-handle filter for a liquid-jet head.

Furthermore, the present invention has been accomplished in the light of the aforementioned situations. It is a further object of the present invention to provide a liquid-jet head including a liquid-jet head filter, which minimizes a pressure loss and ensures an adequate flow rate of ink, which can perform a stable function of trapping foreign matter, and which is easy to handle; and a liquid-jet apparatus equipped with the liquid-jet head.

A first aspect of the present invention for attaining the above object is a die apparatus for boring a through-hole in a work plate, comprising a lower receiving die, a punch, and a flexible member provided between the lower receiving die and the punch, and wherein the punch is passed through the work plate placed on the flexible member to press a punched-out piece into the interior of the flexible member, thereby boring the through-hole in the work plate.

In the first aspect, the punched-out piece is pressed into the interior of the flexible member to bore the through-hole. Thus, there is no need to form the depression for receiving the punch. Nor is it necessary to align the depression with the punch. Accordingly, the work plate having many through-holes formed therein can be easily prepared.

A second aspect of the present invention is the die apparatus according to the first aspect, characterized in that the flexible member is a polymer material.

In the second aspect, the hardness of the flexible material is rendered optimal, so that the punched-out piece can remain within the flexible member. Since the flexible member is the polymer material, moreover, when the punch is brought into contact with the flexible member, the front end of the punch is not damaged.

A third aspect of the present invention is the die apparatus according to the first or second aspect, characterized in that the thickness of the flexible member is twice or more the thickness of the work plate.

In the third aspect, the work plate can be completely passed through, and the punched-out piece can be allowed to remain reliably within the flexible member.

A fourth aspect of the present invention is the die apparatus according to any one of the first to third aspects, characterized in that the surface of the lower receiving die facing the flexible member is flat.

In the fourth aspect, the surface of the lower receiving die is flat. Thus, when many punched-out pieces are pressed into the flexible member, the amounts of indentation are uniform, so that the many punched-out pieces can be reliably kept within the flexible member.

A fifth aspect of the present invention for attaining the aforementioned object is a method for producing a perforated work plate by use of a punch and a lower receiving die, comprising passing the punch through the work plate placed on a flexible member to press a punched-out piece into an interior of the flexible member, thereby boring a through-hole in the work plate.

In the fifth aspect, the work plate having many of the through-holes formed therein can be easily prepared.

A sixth aspect of the present invention is the method for producing a perforated work plate according to the fifth aspect, characterized in that the surface of the lower receiving die facing the flexible member is flat.

In the sixth aspect, the surface of the lower receiving die is flat. Thus, when many of the punched-out pieces are pressed into the flexible member, the amounts of indentation are uniform, so that the many punched-out pieces can be reliably kept within the flexible member, A seventh aspect of the present invention is the method for producing a perforated work plate according to the fifth or sixth aspect, characterized in that the punched-out piece pressed into the interior of the flexible member is allowed to remain in the interior of the flexible member when the punch is pulled out of the flexible member.

In the seventh aspect, when the punch is pulled out of the flexible member, the punched-out piece does not adhere to the punch. Thus, the perforated work plate can be produced satisfactorily.

An eighth aspect of the present invention for attaining the aforementioned object is a perforated work plate formed by the method for producing a perforated work plate according to any one of the fifth to seventh aspects.

In the eighth aspect, the perforated work plate having no flash occurring in the circumferential edge of the hole can be provided.

A ninth aspect of the present invention for attaining the aforementioned object is a liquid-jet head having a pressure generating chamber and a nozzle orifice, and including the perforated work plate according to the eighth aspect for use in a filter for the liquid-jet head which traps foreign matter contained in a liquid to be supplied to the pressure generating chamber.

In the ninth aspect, there can be provided a liquid-jet head having a filter for the liquid-jet head which can more reliably remove foreign matter contained in ink.

A tenth aspect of the present invention is the liquid-jet head according to the ninth aspect, characterized in that the filter for the liquid-jet head is a filter sheet consisting of a metal film alone, has a plurality of the through-holes formed in the filter, and has irregularity lines formed on a surface of the filter, the irregularity lines extending in a lattice pattern.

In the tenth aspect, the filter for the liquid-jet head is a filter having a plurality of the through-holes formed therein. Thus, the resulting liquid-jet head is a liquid-jet head having a filter which ensures the adequate flow rate of ink while minimizing a pressure loss, and which can perform the stable function of trapping foreign matter. Furthermore, the irregularity lines are formed on the surface of the filter. Thus, the liquid-jet head is a liquid-jet head having a filter which eliminates a curling force (residual stress in the bending direction based on the boring of the many through-holes), thereby maintaining a flat state, and thus is easy to handle. In addition, even when mounted in the head, the filter is in a flat state and free from waves, so that changes in the shape of the through-holes due to waves do not occur, and foreign matter in the ink can be reliably removed.

An eleventh aspect of the present invention is the liquid-jet head according to the tenth aspect, characterized in that the size of the through-hole of the filter is the size of the nozzle orifice or smaller.

In the eleventh aspect, clogging of the nozzle orifice with foreign matter can be reliably prevented.

A twelfth aspect of the present invention for attaining the aforementioned object is a liquid-jet apparatus including the liquid-jet head according to any one of the tenth to eleventh aspects.

In the twelfth aspect, there can be provided a liquid-jet apparatus having a filter which ensures the adequate flow rate of ink while minimizing a pressure loss, can perform the stable function of trapping foreign matter, and maintains a flat state, thus facilitating handling.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following descriptions in conjunction with the accompanying drawings.

FIG. 1 is a schematic configurational drawing of an ink-jet recording apparatus.

FIG. 2 is a sectional view of a main portion of an ink-jet head.

FIG. 3 is a sectional view showing the whole of the ink-jet head.

FIGS. 4A and 4B are explanation drawings of a filter.

FIGS. 5A to 5C are explanation drawings of a state of punching.

FIGS. 6A and 6B are operational explanation drawings of a punching step.

FIG. 7 is an operational explanation drawing of a curl-removing step.

FIGS. 8A and 8B are views illustrating the status of formation of irregularity lines.

FIGS. 9A and 9B are explanation drawings of a punch according to another embodiment.

FIGS. 10A and 10B are explanation drawings of a punch according to still another embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An ink-jet recording apparatus, to which a work plate prepared by a method for producing a perforated work plate according to an embodiment of the present invention has been applied as a filter, will be described with reference to FIGS. 1 to 3. A perforated work plate has been prepared using a die apparatus according to an embodiment of the present invention. That is, the perforated work plate is used as a filter for trapping foreign matter contained in a liquid to be supplied to a pressure generating chamber of an ink-jet head.

FIG. 1 shows the schematic configuration of an ink-jet recording apparatus furnished with a liquid-jet head filter formed with the use of a die apparatus according to the present invention. FIG. 2 shows the section of a main portion of an ink-jet head (liquid-jet head). FIG. 3 shows a section showing the whole of the ink-jet head.

An ink-jet recording apparatus (apparatus body) 1 includes an ink-jet head 5 integrated with a carriage 3 installed with an ink cartridge 2, and a recording head 4 mounted on the carriage 3. The carriage 3 is connected to a stepping motor 7 via a timing belt 6, and is guided by a guide bar 8 to reciprocate in the sheet width direction (main scanning direction) of a recording sheet 9. The carriage 3 is in the shape of a box opening upwards, and the recording head 4 is mounted on the carriage 3 such that the nozzle surface of the recording head 4 is exposed at the surface (lower surface) of the carriage 3 opposed to the recording sheet 9. In this state, the ink cartridge 2 is accommodated in the carriage 3.

The recording head 4 is supplied with ink from the ink cartridge 2 and, with the carriage 3 being moved, the recording head 4 ejects ink droplets onto the upper surface of the recording sheet 9, thereby printing images and characters on the recording sheet 9 by dot matrices. Of the numerals in FIG. 1, 10 denotes a cap for sealing nozzle orifices of the recording head 4 during stoppage of printing to prevent drying of the nozzles, and exerting a negative pressure on the nozzle surface of the recording head 4 to perform a cleaning action; 11 denotes a wiper blade for wiping the nozzle surface of the recording head 4; 12 denotes a waste ink reservoir for storing waste ink sucked by the cleaning action; and 13 denotes a control device for controlling the actions of the apparatus body 1.

As shown in FIG. 2, the ink-let head 5 (see FIG. 1) is provided with a control plate 15, and an action signal from the control device 13 (see FIG. 1) is entered into a piezoelectric vibrator 16 (to be described later) via the control plate 15. The control plate 15 is disposed at a site of a head case 18 on a side opposite to a passage unit 17, namely, along the upper surface of the head case 18.

The structure of the recording head 4 will be explained based on FIG. 2.

In the recording head 4, the passage unit 17 is disposed at a front end portion of the recording head 4, and a nozzle plate 19 having nozzle orifices 20 arranged in rows in a nozzle formation surface 19 a is provided in the passage unit 17. A pressure generating chamber 21, which communicates with the nozzle orifice 20 and pressurizes ink by the action of the piezoelectric vibrator 16, is provided, and the pressure generating chamber 21 is supplied with ink from an ink storage chamber 22.

That is, the passage unit 17 comprises the nozzle plate 19, a pressure generating chamber forming plate 24, and a vibration plate 25 laminated together, the nozzle plate 19 having the nozzle formation surface 19 a having the nozzle orifices 20 bored therein; the pressure generating chamber forming plate 24 having formed therein a space corresponding to the pressure generating chambers 21, the ink storage chamber 22 as a liquid storage chamber common to the pressure generating chambers 21, and ink supply paths 23 in communication with the pressure generating chambers 21 and the ink storage chamber 22; and the vibration plate 25 being a sealing plate for sealing the openings of the pressure generating chambers 21 and the ink storage chamber 22. The nozzle formation surface 19 a is a flat surface. The passage unit 17 is joined to the front end surface 18 a of the head case 18 with the use of an adhesive agent.

The piezoelectric vibrator 16 is a vibrator in a so-called longitudinal vibration mode which contracts in a longitudinal direction in a charged stated upon receipt of a drive signal, and expands in the longitudinal direction during the process of discharge from the charged state. The piezoelectric vibrator 16 has a front end secured to an island portion 25 a of the vibration plate 25, which forms a part of the pressure generating chamber 21, and has the other end fixed to a foundation 26. The piezoelectric vibrator 16 in the longitudinal vibration mode may be replaced by a piezoelectric vibrator in a flexural vibration mode.

In the head case 18, a head passage 27 is formed in a portion corresponding to the ink storage chamber 22. Ink of the ink cartridge 2 (see FIG. 1) is introduced into the ink storage chamber 22 via the head passage 27. A flexible circuit plate 28 is connected to the piezoelectric vibrator 16, which receives a drive signal from the control plate 15. A flexible circuit plate 29, which transmits an action signal from the control device 13 (see FIG. 1) for operating the whole of the apparatus body 1 (see FIG. 1) to the control plate 15, is connected to the control plate 15 via a terminal 30.

In the recording head 4, the pressure generating chamber 21 contracts and expands upon the contraction and expansion of the piezoelectric vibrator 16, and the suction of ink and the ejection of ink droplets are performed according to changes in the pressure of the pressure generating chamber 21. The nozzle plate 19 has nozzles formed in plural pairs of rows, each pair being constituted by two rows of the nozzles. A head cover 14 for protecting the nozzle formation surface 9 a is provided. The head cover 14 prevents an unsmooth action, or scars to the corner of the passage unit 17, because of the wiper blade 11 (see FIG. 1) being rubbed against the corner of the passage unit 17 during wiping of the nozzle formation surface 19 a.

Ink fed from the ink cartridge (see FIG. 1) flows from the head passage 27 into the ink storage chamber 22. Then, the ink is pressurized in the pressure generating chamber 21 by the action of the piezoelectric vibrator 16, and is ejected, as ink droplets, through the nozzle orifice 20 toward the recording sheet 9 (see FIG. 1) to proceed with printing.

The entire configuration of the ink-jet head 5 will be described with reference to FIG. 3.

As shown in FIG. 3, the ink-jet head 5 is constructed, with the recording head 4 being coupled to a head holder 41 corresponding to the carriage 3 (see FIG. 1). A plate-shaped member 41 a is disposed in an upper portion of the head holder 41, and ink supply pins 31, which enter the ink cartridge 2 (see FIG. 1), are attached to the plate-shaped member 41 a. A passageway inside the ink supply pin 31 communicates with an introduction passage 33 via a filter 32, and the introduction passage 33 is formed by an introduction pipe 34 provided on the underside of the plate-shaped member 41 a.

An annular protrusion 42 at an upper portion of the head case 18 passes through the control plate 15, and the head passage 27 and the introduction passage 33 are disposed coaxially. The head passage 27 and the introduction passage 33 are connected while being sealed with a packing member 35, and the packing member 35 is composed of an elastic material such as an elastomer. The head case 18 is mounted on the head holder 41 via the packing member 35, whereby the packing member 35 is compressed between the end surface of the introduction pipe 34 and the end surface of the annular protrusion 42. According to such a passage structure, when the ink supply pins 31 are relatively inserted into the ink cartridge 2 serving as a fluid supply source, ink is supplied to the passage unit 17.

The filter 32 provided in the above-described apparatus body 1 is produced by the method for producing a perforated work plate according to an embodiment of the present invention. A die apparatus according to the embodiment of the present invention is used for its production.

The filter 32 will be described with reference to FIGS. 4A and 4B.

FIG. 4A shows a plan illustrating the whole of the filter 32, and FIG. 4B shows an enlarged state of the essential part of the filter 32.

As shown in these drawings, the filter 32 is formed by boring many fine holes 52 (for example, several tens of thousands of the holes/cm², each hole having a diameter of 15 μm), which are through-holes, in a flat work plate (filter sheet: for example, 15 μm in thickness) 51 made of stainless steel (SUS), and cutting the perforated work plate into a circular form. That is, the filter 32 is composed of a filter sheet consisting of a metal film. The diameter of the filter 32 is, for example, of the order of 8 to 9 mm, and the diameter of the fine hole 52 is set to be smaller than that of the nozzle orifice 20 (see FIG. 2).

The hole of the filter 32 may be a square hole or a hexagonal hole. In this case, it suffices for the length of the diagonal line of the hole to be set to be smaller than the nozzle orifice 20 (see FIG. 2).

Irregularity lines 53 extending in a lattice pattern are formed on the flat work plate 51 to eliminate a curling force (residual stress in a bending direction based on the boring of the many fine holes 52), thereby maintaining a flat state. By providing the irregularity lines 53, curls are eliminated, and a flat state is maintained, even in the filter 32 which is ultrathin. Thus, its handling is easy, making it possible to increase productivity during assemblage.

Even when mounted in the ink-jet head 5 (see FIG. 1), the filter 32 is in a flat state, and is not wavy. Thus, changes in the shape of the fine holes 52 due to waves do not occur, so that foreign matter in the ink can be reliably removed.

The pitch of the fine hole 52 with respect to the adjacent fine hole 52 is set to be, for example, of the order of 4 μm. The irregularity line 53 has a ridge height set at a value, for example, of the order of 20 to 50 μm, and has a pitch, with respect to the adjacent irregularity line 53, set to be, for example, of the order of 60 μm.

A die apparatus used for producing the filter 32 will be described with reference to FIGS. 5A to 5C through FIGS. 8A and 8B.

FIG. 5A shows a section of a state in which punching is performed by the die apparatus according to an embodiment of the present invention. FIG. 5B shows a section of a work plate and a flexible member after punching. FIG. 5C shows a plan of the work plate and the flexible member after punching. FIGS. 6A and 6B offer an operational explanation for a punching step. FIG. 7 offers an operational explanation for a curl-removing step. FIGS. 8A and 8B illustrate the status of formation of the irregularity lines.

The configuration of the die apparatus will be described with reference to FIGS. 5A to 5C.

As shown in FIG. 5A, a die apparatus 54 has a round punch tool 57 provided via a stripper 56 above a flat board-shaped lower receiving die 55 having no irregularities formed therein. On the upper surface of the lower receiving die 55, PET (polyethylene terephthalate: polymer material) 58 is provided as a flexible member. The diameter of the front end 57 a (punch) of the round punch tool 57 corresponds to the diameter of the fine hole 52 of the filter 32, and the front end 57 a of the round punch tool 57 is to be inserted into the PET 58. The surface of the lower receiving die 55 facing the PET 58 has no irregularities, and is flat. Thus, when many punched-out pieces 62 of the work plate 51 are pressed into the PET 58, the amount of indentation is uniform, so that the many punched-out pieces 62 can be reliably kept within the PET 58.

As the polymer material for the flexible material, PC (polycarbonate), POM (polyacetal), ABS (ABS resin), and PPS (polyphenylene sulfide) can be used. The hardness of the flexible material can be selected variously according to the thickness of the work plate, the size and pitch of the fine hole, and so forth.

In the above-mentioned die apparatus 54, the work plate 51 is placed on the PET 58, and the front end 57 a of the round punch tool 57 is passed through the work plate 51 to punch the fine hole 52. At this time, the front end 57 a of the round punch tool 57 that has passed through the work plate 51 is inserted into the PET 58, and the punched-out piece 62 remains within the PET 58. That is, states as shown in FIGS. 8B and 5C are observed. Thus, the fine hole 52 can be punched without the need to provide on the die side a depression for receiving the front end 57 a of the round punch tool 57.

The thickness of the PET 58 is at least twice the thickness of the work plate 51, and is preferably of the order of 0.1 mm to 0.2 mm. By adopting such a thickness of 0.1 to 0.2 mm, the punched-out piece 62 can be reliably allowed to remain within the PET 58 without rendering the thickness of the PET 58 larger than necessary. Besides, the work plate 51 can be completely penetrated. Thus, there is no flash occurring at the circumferential edge of the fine hole 52 due to poor penetration.

Hence, the use of the above-described die apparatus 54 enables the fine hole 52 to be bored, with the punched-out piece 62 remaining within the PET 58, Consequently, there is no need to form the depression receiving the front end 57 a of the round punch tool 57. Nor is it necessary to align the depression with the front end 57 a of the round punch tool 57. Accordingly, the work plate 51 having the fine holes 52 formed therein can be easily prepared.

The actions in the punching step will be described with reference to FIGS. 6A and 6B.

As shown in FIG. 6A, the stripper 56 is moved toward the lower receiving die 55, whereby the front end 57 a of the round punch tool 57 is driven into the work plate 51, with the result that the front end 57 a of the round punch tool 57 and the punched-out piece 62 are inserted into the PET 58. The stripper 56 is raised and, with the punched-out piece 62 being left within the PET 58, the work plate 51 is moved, together with the PET 58, by one pitch, whereafter the front end 57 a of the round punch tool 57 is driven into the work plate 51 again. By repeating this action, many of the fine holes 52 are formed in the work plate 51.

As noted above, the operation of moving the work plate 51, along with the PET 58, by one pitch, and driving the front end 57 a of the round punch tool 57 into the work plate 51 is repeated. Thus, even if a burr occurs, there is no possibility for the occurrence of a lateral burr due to the burr being crushed by the end surface of the stripper 56. Incidentally, if a die having a depression for insertion of the front end 57 a of the round punch tool 57 is placed below, and used, the movement of the work plate may result in the crushing of the burr between the upper surface of the die other than the depression and the end surface of the stripper 56, thereby deforming the fine hole 52. The use of the above-described die apparatus 54 is free from the possibility for deformation of the fine hole 52.

If the PET 58 was used, a burr measuring about 4 to 5 μm was seen, but little damage to the round punch tool 57 was confirmed. If PC harder than the PET 58 was used, a burr of the order of 2 to 3 μm was observed. These findings demonstrate that the use of the PET 58 can suppress a burr, and minimize damage to the round punch tool 57. The use of a hard flexible material can reduce a burr.

Actions for a curl-removing step will be described with reference to FIG. 7.

The work plate 51 having many of the fine holes 52 formed therein is punched by an oval product punching die 65 to be formed into the shape of the filter 32. Irregularities 66 for forming the irregularity lines 53 are provided on the opposed surfaces of an upper die 65 a and a lower die 65 b of the oval product punching die 65. Simultaneously with the punching-out of the shape of the filter 32, the irregularity lines 53 (see FIGS. 4A and 4B) are formed on the surface of the filter 32.

As shown in FIG. 8A, the irregularity lines 53 can be formed on the entire surface of the filter 32. Alternatively, as shown in FIG. 8B, the irregularity lines 53 can be formed, with a welding margin 67 being left intact on the periphery of the filter 32.

By using the oval product punching die 65 (see FIG. 7) provided with the irregularities 66 (see FIG. 7), pressurization and correction can be performed at the same time during punching-out of the oval product.

Thus, the above-mentioned filter 32 ensures the adequate flow rate of ink while minimizing a pressure loss, and can perform the stable function of trapping foreign matter. Furthermore, its handling is easy. Hence, it can be used as the filter 32 for the ink-jet head, which traps foreign matter contained in the ink to be supplied to the pressure generating chamber 21 of the ink-jet head 5 having the pressure generating chambers 21 and the nozzle orifices 20.

Other embodiments of the punch will be described with reference to FIGS. 9A, 9B and FIGS. 10A, 10B.

A punch tool 71 shown in FIG. 9A has a plurality of (16 in the illustrated embodiment) square-shaped front end portions 73 (punches) provided on the end surface of a cubic body 72 (pin-implanted holder type) One side of the front end portion 73 is formed with a dimension, for example, of 13 μm, whereas the length of the diagonal line of a fine hole 74 of a work plate 51 is set at about 15 μm, as shown in FIG. 9B. The shape of the front end portion 73 may be circular.

By using the punch tool 71 shown in FIG. 9A, a plurality of (16 in the illustrated embodiment) the fine holes 74 can be formed by single punching.

A punch tool 81 shown in FIG. 10A has a plurality of (5 in the illustrated embodiment) square-shaped front end portions 83 (punches) provided on the end surface of a rectangular parallelopipedal body 82 (comb-toothed type). One side of the front end portion 83 is formed with a dimension, for example, of 13 μm, as with the one shown in FIG. 9A. On the other hand, the length of the diagonal line of a fine hole 84 of a work plate 51 is set at about 15 μm, as shown in FIG. 10B. The shape of the front end portion 83 may be circular.

By using the punch tool 81 shown in FIG. 10A, a plurality of (S in the illustrated embodiment) the fine holes 84 can be formed by single punching.

Accordingly, the use of the punch tools 71 and 81 shown in FIGS. 9A and 10A enables a plurality of fine holes to be formed by single punching, and makes it possible to increase the efficiency of manufacturing without raising the speed of the punching apparatus.

While the present invention has been described by the foregoing embodiments, it is to be understood that the invention is not limited thereby, but may be varied in many other ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the appended claims. 

1. A die apparatus for boring a through-hole in a work plate, comprising a lower receiving die, a punch, and a flexible member provided between the lower receiving die and the punch, and wherein the punch is passed through the work plate placed on the flexible member to press a punched-out piece into an interior of the flexible member, thereby boring the through-hole in the work plate.
 2. The die apparatus according to claim 1, wherein the flexible member is a polymer material.
 3. The die apparatus according to claim 1, wherein a thickness of the flexible member is twice or more a thickness of the work plate.
 4. The die apparatus according to claim 1, wherein a surface of the lower receiving die facing the flexible member is flat.
 5. A method for producing a perforated work plate by use of a punch and a lower receiving die, comprising passing the punch through the work plate placed on a flexible member to press a punched-out piece into an interior of the flexible member, thereby boring a through-hole in the work plate.
 6. The method for producing a perforated work plate according to claim 5, wherein a surface of the lower receiving die facing the flexible member is flat.
 7. The method for producing a perforated work plate according to claim 5, wherein the punched-out piece pressed into the interior of the flexible member is allowed to remain in the interior of the flexible member when the punch is pulled out of the flexible member.
 8. A perforated work plate formed by the method for producing a perforated work plate according to claim
 5. 9. A perforated work plate formed by the method for producing a perforated work plate according to claim
 6. 10. A perforated work plate formed by the method for producing a perforated work plate according to claim
 7. 11. A liquid-jet head having a pressure generating chamber and a nozzle orifice, and including the perforated work plate according to claim 8 for use in a filter for the liquid-jet head which traps foreign matter contained in a liquid to be supplied to the pressure generating chamber.
 12. The liquid-jet head according to claim 11, wherein the filter for the liquid-jet head is a filter sheet consisting of a metal film alone, has a plurality of the through-holes formed in the filter, and has irregularity lines formed on a surface of the filter, the irregularity lines extending in a lattice pattern.
 13. The liquid-jet head according to claim 12, wherein a size of the through-hole of the filter is a size of the nozzle orifice or smaller.
 14. A liquid-jet apparatus including the liquid-jet head according to claim
 12. 15. A liquid-jet apparatus including the liquid-jet head according to claim
 13. 